Signal transduction is any process by which a cell converts one kind of signal or stimulus into another. Processes referred to as signal transduction often involve a sequence of biochemical reactions inside the cell, which are carried out by enzymes and linked through second messengers. In many transduction processes, an increasing number of enzymes and other molecules become engaged in the events that proceed from the initial stimulus. In such cases the chain of steps is referred to as a “signaling cascade” or a “second messenger pathway” and often results in a small stimulus eliciting a large response. One class of molecules involved in signal transduction is the kinase family of enzymes. The largest group of kinases are protein kinases, which act on and modify the activity of specific proteins. These are used extensively to transmit signals and control complex processes in cells.
Protein kinases are a large class of enzymes which catalyze the transfer of the γ-phosphate from ATP to the hydroxyl group on the side chain of Ser/Thr or Tyr in proteins and peptides and are intimately involved in the control of various important cell functions, perhaps most notably: signal transduction, differentiation, and proliferation. There are estimated to be about 2,000 distinct protein kinases in the human body, and although each of these phosphorylate particular protein/peptide substrates, they all bind the same second substrate, ATP, in a highly conserved pocket. Protein phosphatases catalyze the transfer of phosphate in the opposite direction.
A tyrosine kinase is an enzyme that can transfer a phosphate group from ATP to a tyrosine residue in a protein. Phosphorylation of proteins by kinases is an important mechanism in signal transduction for regulation of enzyme activity. The tyrosine kinases are divided into two groups; those that are cytoplasmic proteins and the transmembrane receptor-linked kinases. In humans, there are 32 cytoplasmic protein tyrosine kinases and 58 receptor-linked protein-tyrosine kinases. The hormones and growth factors that act on cell surface tyrosine kinase-linked receptors are generally growth-promoting and function to stimulate cell division (e.g., insulin, insulin-like growth factor 1, epidermal growth factor).
Inhibitors of various known protein kinases or protein phosphatases have a variety of therapeutic applications. One promising potential therapeutic use for protein kinase or protein phosphatase inhibitors is as anti-cancer agents. About 50% of the known oncogene products are protein tyrosine kinases (PTKs) and their kinase activity has been shown to lead to cell transformation.
The PTKs can be classified into two categories, the membrane receptor PTKs (e.g. growth factor receptor PTKs) and the non-receptor PTKs (e.g. the Src family of proto-oncogene products). There are at least 9 members of the Src family of non-receptor PTKs with pp60c-src (hereafter referred to simply as “Src”) being the prototype PTK of the family wherein the approximately 300 amino acid catalytic domains are highly conserved. The hyperactivation of Src has been reported in a number of human cancers, including those of the colon, breast, lung, bladder, and skin, as well as in gastric cancer, hairy cell leukemia, and neuroblastoma. Overstimulated cell proliferation signals from transmembrane receptors (e.g. EGFR and p185HER2/Neu) to the cell interior also appear to pass through Src. Consequently, it has recently been proposed that Src is a universal target for cancer therapy, because hyperactivation (without mutation) is involved in tumor initiation, progression, and metastasis for many important human tumor types.
Cancer cells are by definition heterogeneous. For example, within a single tissue or cell type, multiple mutational “mechanisms” may lead to the development of cancer. As such, heterogeneity frequently exists between cancer cells taken from tumors of the same tissue and same type that have originated in different individuals. Frequently observed mutational “mechanisms” associated with some cancers may differ between one tissue type and another (e.g., frequently observed mutational “mechanisms” leading to colon cancer may differ from frequently observed “mechanisms” leading to leukemias). It is therefore often difficult to predict whether a particular cancer will respond to a particular chemotherapeutic agent (Cancer Medicine, 5th edition, Bast et al., B. C. Decker Inc., Hamilton, Ontario).
Malignant gliomas cause over 15,000 cancer deaths in the United States each year. These brain tumors are among the most difficult human cancers to treat, even with extensive surgery, radiation therapy and chemotherapy, survival remains poor. The most widely used chemotherapy drug for treating glioma patients is Temodar (Temozolamide). Even with the best current therapy available the probability that a glioblastoma patient will survive at least two years is 9%. Brain edema is also a serious problem for these brain cancer patients and they often require treatment with corticosteroids to reduce the edema, but are then subjected to the common steroidal side effects of immunosuppression, hypertension and steroidal dependence. A major challenge in developing new therapies for treating gliomas and brain metastases is that very few small molecule anti-tumor drugs are capable of penetrating the brain well enough to provide therapeutically effective drug levels. Consequently, the development of more effective drugs for treating brain cancer and brain metastases is a large unmet medical need. The present invention addresses these needs.
Because kinases are involved in the regulation of a wide variety of normal cellular signal transduction pathways (e.g., cell growth, differentiation, survival, adhesion, migration, etc.), kinases are thought to play a role in a variety of diseases and disorders. Thus, modulation of kinase signaling cascades may be an important way to treat or prevent such diseases and disorders.
There is a need for compositions and processes for the synthesis of highly purified compound 1, which is safe and simple and which produces compound 1 on a large scale in high yield and which is substantially free of impurities.